the dehydrogenation of 16alpha-methyl-11beta,17alpha,21-trihydroxypregna-1,4-diene-3,20-dione-21-acetate (i) with dichlorodicyanobenzoquinone (ii) in dioxane hcl gives 16alpha-methyl-11beta,17alpha,21-trihydroxypregna-1,4,6-triene-3,20-dione-21-acetate (iii), which is hydrolyzed with aqueous nahco3 to the corresponding free triol (iv). the reaction of (iv) with triethyl orthopropionate (a) by means of p-toluenesulfonic acid in dmso yields 16alpha-methyl-11beta,17alpha,21-trihydroxypregna-1,4,6-triene-3,20-dione-17,21-ethylorthopropionate (v), which is hydrolyzed partially with acetic acid to 16alpha-methyl-11beta,17alpha,21-trihydroxypregna-1,4,6-triene-3,20-dione-17-propionate (vi). the acylation of (vi) with propionic anhydride affords 16alpha-methyl-11beta,17alpha,21-trihydroxypregna-1,4,6-triene-3,20-dione-17,21-dipropionate (vii), which is finally treated with dry hcl in dioxane.

the dehydrogenation of 16alpha-methyl-17alpha,21-dihydroxypregna-1,4-diene-3,11,20-trione-21-acetate (viii) with (ii) in dioxane-hcl gives 16alpha-methyl-17alpha,21-dihydroxypregna-1,4,6-triene-3,11,20-trione-21-acetate (ix), which is hydrolyzed with aqueous nahco3 to the corresponding free diol (x). the reaction of (x) with triethyl orthopropionate (a) as before yields 16alpha-methyl-17alpha,21-dihydroxypregna-1,4,6-triene-3,11,20-trione-17,21-ethylorthopropionate (xi), which is hydrolyzed partially with acetic acid to 16alpha-methyl-17alpha,21-dihydroxypregna-1,4,6-triene-3,11,20-trione-17-propionate (xii). the acylation of (xii) with propionic anhydride yields the corresponding dipropionate (xiii), which is treated with dry hcl in dioxane to afford 16alpha-methyl-17alpha,21-dihydroxy-7alpha-chloropregna-1,4-diene-3,11,20-trione 17,21-dipropionate (xiv). finally, this compound is reduced with nash4 in methanol - thf.